To be honest, I don't think it's all that hard to believe.
[All of the sweet, supposedly kind children he had spoken to had all turned out to have killed someone. He knew all too well he couldn't trust anyone here, not even this girl who seemed to have a lot in common with him.]
Ah, well, I love the sport! So if you want me to explain you might be in for a bit of a lecture. Would you like me to continue?